Playing lots of Destiny 2 since its release. Haven't finished the campaign yet, but have reached lvl 20 and about 250 power(=light) already. This is very overpowered for the campaign, but since D2 PvE is vastly improved over D1 PvE, exploring the sandbox (if you can call it that) along the way for chests and 'lost sectors' (like semi-hidden mini boss arenas) for loot levels you rather fast. The character lvl is kinda moot, and probably only applies to the first 5 hours of playing, gating some gear and abilities progress. Real long term progression target is in the 'power' stat, which is basically the level of your gear, and it slows way down in end game. But what makes the most difference is actually weapon perks (and the style of the sights), and now also weapon/gear mods in D2. These directly affect how your weapon/character handles, and getting new gear is the bread and butter of Destiny, for cosmetics or otherwise!
I have the most fun in PvP though, so if you don't like that, then the game will probably get stale fast after you have finished the campaign. My end game looks something like this:
Play PvP for fun --> get murdered --> grind PvE activities for better performing or better looking loot --> return to PvP for fun/getting murdered. Repeat with different class.
There are enough guns, gear, and character classes (BRING ON THE 4TH CHARACTER CLASS!!!) for a very long gameplay lifetime, but PvP is still my reason to keep playing Destiny.